A lot of women who have had babies claim that their mental abilities declined during and immediately after pregnancy. They tell of losing the car keys, walking into a room and not remembering why that have gone there, forgetting people's names and finding that they easily lose their train of thought part way through a sentence. Famous mothers Kate Winslet and Myleene Klass, both of whom have suffered in this way have referred to the condition as "baby brain" or "preg head". But is the condition real or just imaginary?

In 2008 a researcher at the University of NSW and Australian Catholic University amalgamated the data from 14 separate studies into cogitative impairment during pregnancy. By combining these studies they were able to compare the memory performances of more than 1,000 pregnant women, new mothers and healthy women who were not pregnant.

The study revealed that up to 80% of mothers believe that they suffered from "baby brain" during pregnancy and for approximately a year afterwards with the most common symptom being increased forgetfulness.

Julie Henry, one of the study's authors said that the effect was "very, very subtle" but that "the results indicate that pregnant women are significantly impaired on some, but not all, measures of memory." The study found that this reduction in mental capacity particularly affected the higher order cerebral functions of the brain.

In a separate study led by Professor Helen Christensen, of the Australian National University in Canberra, researchers studied 2,500 women aged from 20 to 24, first in 1999 and then again in 2004 and 2008.

The study found that women who were pregnant during the second or third series of interviews performed the same on tests of logic and memory as they did before, and that there was no difference between the pregnant women and the non-pregnant women.

In yet another study conducted by Dr Craig Kinsley of Richmond University in Virginia in 2008, he found that far from debilitating the brain, that giving birth supercharges brainpower to equip women for the challenge of rearing their child.

He believes having a baby produces a surge of memory and learning ability that makes women more vigilant and alert.

It is known for instance that hormonal fluctuations during birth and breastfeeding increase the size of cells in some areas of the brain, leading to dramatic improvements in mental capacity.

Studies on animals including rats and primates found mothers become much braver, are up to five times faster at finding food and have better spatial awareness than those without offspring.

Dr Kinsley said: "While a woman may experience an apparent loss of brain function while she is pregnant, this could be because parts of her brain are being remodelled in preparation for dealing with the complicated demands of child-rearing."

Three different studies, three different conclusions, is it possible that they could all be correct?

Our own hypothesis at MyBrain is that it would be logical if evolution had equipped women to be more protective during pregnancy and more empathetic and responsive to a baby's needs in its early years of life when it will be entirely dependant on the support of adults for its survival. Since both of these instincts reside in the limbic or mammalian brain
it may be that pregnancy causes women to divert more of their mental processing capacity to those parts of the brain. If this were the case it may also help to explain why many women notice a reduction on the cognitive abilities that rely more on the functioning of the cerebral or upper part of the brain.

There is some anecdotal evidence to support this as we do observe a tendency of people who have completed Brain Dominance profiles before and after pregnancy to become slightly more limbic in the later ones.

Please click here to visit the related Brain Blog where you can add your anecdotes and experiences to the discussion.